What is the difference between IF-ELSE and SWITCH?

They are pretty similar but each has a few special features.

switch

• switch is usually more compact than lots of nested if else and therefore, more readable
• If you omit the break between two switch cases, you can fall through to the next case in many C-like languages. With if else you'd need a goto (which is not very nice to your readers ... if the language supports goto at all).
• In most languages, switch only accepts primitive types as key and constants as cases. This means it can be optimized by the compiler using a jump table which is very fast.

• It is not really clear how to format switch correctly. Semantically, the cases are jump targets (like labels for goto) which should be flush left. Things get worse when you have curly braces:

  case XXX: {
  } break;
  

  Or should the braces go into lines of their own? Should the closing brace go behind the break? How unreadable would that be? etc.

• In many languages, switch only accepts only some data types.

if-else

• if allows complex expressions in the condition while switch wants a constant
• You can't accidentally forget the break between ifs but you can forget the else (especially during cut'n'paste)
• it accepts all data types.

The main difference is that switch despatches immediately to the case concerned, typically via an indexed jump, rather than having to evaluate all the conditions that would be required in an if-else chain, which means that code at the end of the chain is reached more slowly than code at the beginning.

That in turn imposes some restrictions on the switch statement that the if-else chain doesn't have: it can't handle all datatypes, and all the case values have to be constant.