Edit dosbox.conf in your DOSBox folder.

You mean how they work? The normal core does the usual interpretation
cycle (fetch next instruction, executing it), the dynamic core does dynamic
recompilation (translate a block of instructions if it's not in the cache,
execute that block).

What is the advantagesof dynamic core and what are the advantages of using simplae or full core.

The full core is only used internally as it's slower but has certain nice
characteristics. Dynamic core is pretty fast but only available on x86 systems,
the simple core has faster decoding (but is incompatible with one or two games).

what do you mean by fast decoding

When fetching the next instruction it uses a pretty direct way to grab
the bytes from memory, rather than using the regular memory functions.
The simple core doesn't work together with paging and stuff, dosbox
switches to the normal core then.