I'd link you to the tutorial about it but it seems that site is down. :/
altaction_4 is what "altaction" does when your curweapon is 4 (SMG). By default it contains "quicknadethrow".
"domodifier" changes alias "modifier" to the supplied argument, which in turn causes your mouse wheel (again, by default) to modify "delta_" settings.
For your question, "domodifier 1" sets the modifier to 1, which causes the mouse wheel to modify delta_game_1, delta_spect_1, and delta_edit_1 (depending on whether you're alive, spectating, or editing) +1 or -1 at a time when scrolling. By default, this is activated by holding down 1 while scrolling.
I can't see any default definition for when you're alive or spectating with domodifier 1 (delta_game_1 and delta_spect_1)...
delta_edit_1 changes heightfield vdelta values.
altaction_4 is what "altaction" does when your curweapon is 4 (SMG). By default it contains "quicknadethrow".
"domodifier" changes alias "modifier" to the supplied argument, which in turn causes your mouse wheel (again, by default) to modify "delta_" settings.
For your question, "domodifier 1" sets the modifier to 1, which causes the mouse wheel to modify delta_game_1, delta_spect_1, and delta_edit_1 (depending on whether you're alive, spectating, or editing) +1 or -1 at a time when scrolling. By default, this is activated by holding down 1 while scrolling.
I can't see any default definition for when you're alive or spectating with domodifier 1 (delta_game_1 and delta_spect_1)...
delta_edit_1 changes heightfield vdelta values.