There are size and character limits on DNS, so it's not infinite, although it may still be a pretty large space. Charts.(something well known) could have been a dictionary check though.
Ah, I totally forgot about the domain name (255) and label (63) length limits: thanks!
Still, we are looking at roughly 38*255 possible options (a-z, 0-9, a hyphen and dot to separate labels; "roughly" because each label between periods can be up to 64 characters, labels must be non-empty, and hyphens can't start a label).
As you said, it's pretty large: compared to 2*32 of IPv4 or even 2*128 of IPv6, this is more than (2*5)*255 = 2*1275 options.
Still, we are looking at roughly 38*255 possible options (a-z, 0-9, a hyphen and dot to separate labels; "roughly" because each label between periods can be up to 64 characters, labels must be non-empty, and hyphens can't start a label).
As you said, it's pretty large: compared to 2*32 of IPv4 or even 2*128 of IPv6, this is more than (2*5)*255 = 2*1275 options.