Is there something I can do in string to make sure it contains letters/numbers and not just spaces?

I was wondering if there is anything I can do with a string to make sure that a player has entered letters/numbers and not just put a bunch of spaces.

Keep in mind, this is not a request site. You can easily look this stuff up. string.gsub is what you're looking for I believe. This will remove all whitespace. I found this example over a quick google search:

local function RemoveSpaces(str)
    return str:gsub(" ","")
end

Read about Strings here.