The Serengeti is a large park stretching from the Ngorongoro Conservation Area, all the way out to Lake Victoria and up as far as the Kenyan border.  The migratory animals range across this whole area.

 

Which areas of the Serengeti you visit is critical and will depend on when you are travelling.  This can make a huge difference to what you see;  on the one hand this could be massed herds of wildebeest, on the other it could be hordes of tourists.

 

There are some excellent camps and lodges in the Serengeti from luxury lodges, to seasonal mobile camps and - if you don't mind helping stick up your tent to save a bit of money - an excellent light mobile camping option.