Lol -- great joke! The capitalized words are all names of computer programs from Microsoft. “Word” (word-processing) “Excel” (spreadsheet / calculations) and “Powerpoint” (presentations) are all components of ”Microsoft Office” (an office productivity suite). To “excel” is also a common verb meaning to do very well, and “word” is slang meaning something you “that’s true.” A "pun" is a play on words.

Not "jork," but "joke." This joke is based on a "pun," which uses words that can express multiple meanings and can have a humorous effect. The words that are being used in the joke are "Excel" and "Word." Both Excel and Word are titles of two different Microsoft office programs (as is powerpoint too), as you probably already know (not sure if they maintain those names where you are from). However, the word "excel" can also mean to be successful with something or to be good at something. Finally, when the speaker says "word" at the end, this is also a pun on the Microsoft Office theme, because "word" is yet another program, but it is also used as a slang to agree with something. It's like saying "yeah," but it's not often used these days. Does this make it clearer? Let me know if you are still confused.

To *excel* at something, means to be good at it.