Filters allow you to create rules about what should happen to certain emails in your mailbox. The best thing is, once you set up a filter, this will happen automatically - you don't have to do anything.
Filters are created for a variety of reasons. It could be because of the sender, the recipient, certain keywords in the body or subject of the email, a combination of these factors, etc.
There are a few ways to create a filter. One way is to create an email from an existing email. Find an email that you'd like to filter and then click "More" across the top. Click on "Filter messages like these".
Now you can choose the criteria you wish to use to filter your email. Sender, recipient, keywords in the subject or body, whether or not it has an attachment, etc. You can use as many or as few of these criteria as you need. Once you are finished, click "Create filter with this search" in the bottom right.
This will take you to a window where you decide what you'd like Gmail to do with the emails you are filtering. Do you want to delete them? Archive them so they come up in searches, but won't clutter your inbox? Have them automatically be labeled once they arrive? There are a variety of things you can specify in this window. Once you have made your choices, you can click "Create filter" in the bottom left.
That's it! Now your filter is created and you can sit back and know that Gmail will filter your messages automatically.
You can also create a new filter by clicking on the little down arrow in the search bar across the top of your inbox. You can fill out the search criteria and click "Create filter with this search" just like you did in the steps above.
If you'd like to edit or delete your filters, click on the gear icon in the upper right corner of your inbox and choose "Settings" from the menu.
Across the top of the settings window, click on "Filters and Blocked Addresses". Here you can see a list of all your filters, edit them, or delete them. You can also create new filters by clicking the "Create a new filter" link.