If you dont undrstand history you relay dont understand maya. Much more complex than photoshop history tahts just a glorified undo queue realy.
What you should do is read the manual.
OK time to open up hypergraph then slect the object and hit graph upsterams and downstreams icon while a object is selected.
se the line of stuff, its all recorded what youve done to the object, you can go back delete tweaks in between, diverge other shapes and such.
Begin simple take a cube notice how its history is a create that connects to the shape, now you can edit how many sections the cube has.
Now extrude one face notice how a extrusion appears between the shape and the create node, now you can edit the extrude. Now extrude the extrude. Then select the dfirst extrude closest to the create thing. and edit it. Note how maya remebers what youve built on top.
So what happens is maya has everything youve done to all these nodes recorded and pased on so you can go back in history and edit things.
Drawback is that history uses memory, also if you do changes something in the beginning of history everything down the line must be regenerated wich can be slow if you have accumulkated history since the begging of dawn.
Dont keep history you dont need. If you dont know what history is then you dont need it. Period
If this explanation and experimentation doesnt give you a clue on whats going on them im afraid i cant help you.
But its waaay more complex than that you can split up the history say to make a object thats looks like what another object looked in step 5 and build some own history for that object on top of that form step 5 forward while the other object continues in a different direction form there.... etc etc.
Read the manual its all there but im afraid to undertand this fully you need to grasp the entire manual.
ok i need sleep.