Using IPFS as a viewer requires no extra software becuase of the gateways.
To help seed content and ensure the existence of our files some may want to run an instance themselves and redirect ipfs links on the internet to their local instance. Then after viewing the file they are also a seed.
To do this you need two things. You need the IPFS software https://ipfs.io/docs/install/ and the browser addon https://addons.mozilla.org/en-US/firefox/addon/ipfs-companion/
Follow the instructions for installation and then run ipfs when ever you like by opening the terminal and typing
Next you just need the browser addon
It should detect when you have the daemon running and redirect only when it makes sense.
Which is more performant? Using the local instance and companion can handle higher bandwidth and removes any issue of a gateway having issues (though that is rare). The downside is that the companion uses blocking code and that can be visible.