Debounce program question

[EBCrp]

SOLVED! page 40 (Listing 2-5) - "if (last != current)". I understand the use of the function but I cannot figure out where the program is finding the "last" from. I can see conceptually where the last value is coming from but I cannot figure out from a program standpoint how it is getting this value. Is "last" a keyword in arduino because other than the function itself I don't see it ever defined. Obviously the program understands it so it is clearly only me!! Sorry if this is not the right place to put such comments.