What is the difference between Pascal Case and Camel Case?

Pascal case is a subset of Camel Case where the first letter is capitalized.

That is, userAccount is a camel case and UserAccount is a Pascal case.

The conventions of using these are different. You use camel case for variables and Pascal case for Class names or Constructors.

It is easy to remember. Pascal is a proper noun so capitalize the first letter.
camel is a common noun, so you do not capitalize the first letter.

Talking from a programmer's perspective, PascalCase means the first char should be capitalized while camelCase means the first char should be lowercased.

To remember camel case you have to think about the shape of the capital letters. They are like the humps of a camel as you can see this image.

Pascal Casing - capitalizes each word:

ThisShouldBePascalCase

Camel Casing - is similiar to pascal case but the first word is not capitalized:

thisShouldBeCamelCase

In general both can be considered equivalent although by definition "CamelCase" is a valid camel-cased word. Hence, PascalCase can be considered to be a subset of camelCase.