Kindles (especially the earlier ones) can be a little more "locked down" as far as what apps it can use and other functionality. As JJ said, it really depends on which model you have.
For example Android pretty much expects you to use "Google Play" as the primary source for your apps. They make it a little tricky, but not impossible to use Amazon's App Store. And I'd assume neither of the above can be used on an iPad, leaving you only with the Apple's app Store.
Some of the earlier Kindles were really geared toward just eBooks. And what models that did have any web type access would use a pretty crappy proprietary web browser.
Ideally you want to have the freedom to choose in order to have the most flexibility. You can always google or use youtube to see what workarounds might be available for your model.
Oh, and I love Amazon's "Free App of the Day". I check it every day. They offer one free full version of a paid app each day (vs the free, cut down ad-ridden trial versions). Though I could never have them all installed at once, I've got hundreds in my Amazon e-cloud that I can install any time.
You don't have to use them to "
buy" them. You just click "Get it Now" and it sits in your "Amazon Digital Purchases" cloud until you're ready to install. You can also uninstall & reinstall as often as you like. Amazon also keeps them up to date whenever any updates come out for a particular app.
Be sure to read the
reviews though, some are ridden with spyware.