jQuery was developed in a time, when every browser had it's own way achieving the same thing. For example event listeners, or XMLHttpRequests (aka AJAX).
jQuery provided a really easy way to deal with these x-browser problems. They added a ton of helpful features, too. And that plugin system alone was good enough to take developers hearts by storm.
jQuery never intended to be anything else than a great tool belt, though.
In 2015, almost everything you can do with jQuery, can be done natively with javascript in modern browsers (>=IE9). Domqueries, ajax, events, animations... and there are tons of micro frameworks you can use without including jQuery. I still use jQuery from time to time, as it's very well tested and supported.
Angular on the other hand is a fully fledged javascript/html app framework with data binding and all that crazy stuff.
If you have to implement some ui related actions inside Angular for example, it's your decision if you need jQuery for that.