This is where most of the action takes place. Since I wouldn't want you to miss any of the action, here's an item-by-item rundown:
Reset
This is the same as pressing "reset" on a real II. Or control-reset on a II+, if you were the cautious type. Incidentally, the same can be accomplished by "control-delete"; a cold boot can be done by "control-option-delete". Ok, there you go, a concession to the //e crowd.
Halt
This brings the computer to a halt; it has no common counterpart in the real Apple II world. Handy for games without pause commands.
Step
Single-steps the emulated processor. If you have the disassembly window up and the "Do disassambly" option on, you get to see what instruction is about to get executed. Jim says he can't think of a time that you'd want to single-step without seeing what's happening.
Run
This is the really important one. Sets the emulation to running; useful as a counterpart to "Halt".
Do disassembly
This shows every instruction as it's executed; the display comes up in the disassembly window (imagine that…). Slows the processor down significantly.
Monitor
Jumps to the monitor; this can get you out of the occasional jam. Doesn't bother to set any kind of rational video mode, though.
2x video size
This doubles the size of the video window, which is good for the eyes but bad for emulator performance. Your choice.
Monochrome video
Cheesy for a number of reasons, not the only one of which is that low-res still comes out in color. Improves legibility in some cases, like when there's lots of text on the hi-res screen.
Limit Speed
If you're having trouble with your computer running too fast (oh, to have problems like that…), you can regulate speed here.
