Let me google that for you <---click it
jk,
in a nutshell:
a lower vm heap value means faster switching between small apps, but may cause bigger applications to crash, and possibly better battery. find a value that works for you other than the default
max events, say you set it to 120, once the RAM usage reaches that point the system will start closing process, apps, etc to make the value go under you set value (120). the bigger that value the more apps you can have 'open' at the same time but if running RAM the phone will slow down, the lower the value your phone will never run out of RAM, but you wont be able to have that many apps running.
perhaps im wrong, but thats the general idea.