ok so domain means the set of numbers you are alowed to use
bsaically
domain=all real numbers except for those that make strange things happen
strange things are
1. dividing by zero
2. taking square root of negative
3. might be more, dunno
example
if y ou have
f(x)=3/x, domain is all real number except 0 since if x=0, then 3/0 is undifined
f(x)=3/(2+x), domain is all real except x=-2
for the negative sqrt
f(x)=√x, x cannot be negative, it goes from zero to positive infinity
f(x)=√(x-1), x cannot be less than 1, it has to be any number more than or equal to 1 (√0=0)
basically domain=all real number except for ones that make function comlex or undefined
