How to get the object mouse hits in workspace?

1.) Target property

The mouse has a property called Target, which is a part the player's mouse hits.

game:GetService('RunService').RenderStepped:Connect(function()
    print(player:GetMouse().Target ~= nil and player:GetMouse().Target.Name or 'no target') -- prints the name of the object the player's mouse hits or 'no target' if it doesn't hit anything
end)

2.) Rays

This is pretty much how the Mouse.Target property gets the part that hits the workspace. You need to shoot a ray from the Mouse's Origin(a CFrame positioned at the camera and oriented to where the player's mouse is).

local ray = Ray.new(
        Mouse.Origin.p,
        Mouse.UnitRay.Direction * 50
)

local hit = workspace:FindPartOnRay(ray, character)

print(hit ~= nil and hit.Name or 'no part')

I know someone have answered, but I want to help you in the same way.

You can see of Mouse in Roblox Wiki > Roblox Wiki Page - Mouse

Also you can see Mouse.Target in Roblox Wiki > Roblox Wiki Page - Mouse.Target

Also you can see Mouse.Button1Down in Roblox Wiki > Roblox Wiki Page - Mouse.Button1Down

And you can see Mouse.Hit in Roblox Wiki > Roblox Wiki Page - Mouse.Hit

You only can get Mouse in LocalScript, for get in Server, you need to use a Remote Events

For get position you can use Mouse.Hit.p For get object you need to use Mouse.Target

Local Script - player:GetMouse():

local player = game.Players.LocalPlayer
local Mouse = player:GetMouse()

-- you can use Mouse.Move >

Mouse.Move:Connect(function()
    if Mouse.Target ~= nil and Mouse.Hit.p ~= nil then
        warn("Name: " .. tostring(Mouse.Target) .. "\nPosition: " .. tostring(Mouse.Hit.p))
    else
        warn("The mouse target is nil!")
    end
end)

-- or you can use RunService > RenderStepped, but is not equal of Mouse.Move, RenderStepped is "basicaly a loop"!

game:GetService("RunService").RenderStepped:Connect(function()
    if Mouse.Target ~= nil and Mouse.Hit.p ~= nil then
        warn("Name: " .. tostring(Mouse.Target) .. "\nPosition: " .. tostring(Mouse.Hit.p))
    else
        warn("The mouse target is nil!")
    end
end)

Or you can get Mouse with a Tool Local Script - Tool:

-- You can get mouse in Tool.Equiped

local player = game.Players.LocalPlayer
local mouse = player:GetMouse()
local Tool = script.Parent

-- For use in Tool.Actived you need to use player:GetMouse()

Tool.Activated:Connect(function()
    print(mouse)
    mouse.Move:Connect(function()
        if mouse.Target ~= nil and mouse.Hit.p ~= nil then
            warn("Name: " .. tostring(mouse.Target) .. "\nPosition: " .. tostring(mouse.Hit.p))
        else
            warn("The mouse target is nil!")
        end
    end)

    -- or you can use RunService > RenderStepped, but is not equal of Mouse.Move, RenderStepped is "basicaly a loop"!

    game:GetService("RunService").RenderStepped:Connect(function()
        if mouse.Target ~= nil and mouse.Hit.p ~= nil then
            warn("Name: " .. tostring(mouse.Target) .. "\nPosition: " .. tostring(mouse.Hit.p))
        else
            warn("The mouse target is nil!")
        end
    end)
end)

-- For use in Tool.Equiped you can use Tool.Equiped:Connect(function(MOUSE)

Tool.Equipped:Connect(function(Mouse)

    -- you can use Mouse.Move >

    Mouse.Move:Connect(function()
        if Mouse.Target ~= nil and Mouse.Hit.p ~= nil then
            warn("Name: " .. tostring(Mouse.Target) .. "\nPosition: " .. tostring(Mouse.Hit.p))
        else
            warn("The mouse target is nil!")
        end
    end)

    -- or you can use RunService > RenderStepped, but is not equal of Mouse.Move, RenderStepped is "basicaly a loop"!

    game:GetService("RunService").RenderStepped:Connect(function()
        if Mouse.Target ~= nil and Mouse.Hit.p ~= nil then
            warn("Name: " .. tostring(Mouse.Target) .. "\nPosition: " .. tostring(Mouse.Hit.p))
        else
            warn("The mouse target is nil!")
        end
    end)

end)

Get on server: Create a RemoteEvent put in ReplicatedStorage name as "MouseEvent" (You can change.) Insert a script on ServerScriptService and put:

local event = game:GetService("ReplicatedStorage").MouseEvent -- Location of event

-- You cannot get Mouse with Remote Event, but you can get positions.

event.OnServerEvent:Connect(function(p,hit_pos,hit_target) -- Get player,hit pos, hit target
    if hit_pos ~= nil and hit_target ~= nil then -- If not nil then
        warn("Name: " .. tostring(hit_target) .. "\nPosition: " .. tostring(hit_pos)) -- Print name and position
    else
        warn("The mouse target is nil!") -- Print nil
    end
end)

Now insert a LocalScript and put it on StarterGui and put it:

local plr = game.Players.LocalPlayer -- Get player
local Mouse = plr:GetMouse() -- Get player mouse

local event = game:GetService("ReplicatedStorage").MouseEvent -- Event location

-- you can use Mouse.Move

Mouse.Move:Connect(function()
    event:FireServer(Mouse.Hit.p,Mouse.Target)
end)

-- or you can use RunService > RenderStepped, but is not equal of Mouse.Move, RenderStepped is "basicaly a loop"!

game:GetService("RunService").RenderStepped:Connect(function()
    event:FireServer(Mouse.Hit.p,Mouse.Target)
end)

For detect click you need to use Mouse.Button1Down Example:

local plr = game.Players.LocalPlayer -- Get player
local Mouse = plr:GetMouse() -- Get player mouse

Mouse.Button1Down:Connect(function()
    if Mouse.Target ~= nil and Mouse.Hit.p ~= nil then
        warn("Name: " .. tostring(Mouse.Target) .. "\nPosition: " .. tostring(Mouse.Hit.p))
    else
        warn("The mouse target is nil!")
    end
end)