One of the most important features of any email software is the ability for it to do the work of sorting your mail for you automatically.  Gmail calls this feature 'Filters', and they are essentially a set of actions to take with an email based on selection criteria you specify.

Follow steps below to see examples of creating filters.

1.  By far, the easiest way to create a filter is to base it on an existing email.  To do this, open an email that's of the type that you'd like to 'file'.  In my example, I've selected a message from my team leader.  

Next, click the 'vertical ellipsis' button (three vertical dots) in the upper-right-hand corner of the message window.

2.  From the menu that appears, select 'Filter messages like this'.

3.  A window will appear showing the criteria by which messages will be selected for action.  By default, Gmail assumes you'd like to filter messages that come from a particular email address.  Since this is what I want, we'll move forward.

Note that there are many other criteria that you could apply, if desired.

Click 'Create filter'.

4.  In the next window, you specify what the filter should do with the messages it selects.  My goal is to simply automatically tag these messages with a label.

So, I put a check in the box next to 'Apply the label', and select the label I'd like from the pulldown.

Note that there are many other actions that you could take, also.

Since I'm sure that's all I want the filter to do, I then click 'Create filter'.

5.  Now, all new messages that arrive from my team leader will get the 'Leadership' label.  If I'd like to stop that happening, I can go to my filters list, and delete that filter.

To do that, I click on the 'Settings' icon (looks like a gear), and select the 'Settings' command.

6.  In the Settings window, select the 'Filters and Blocked Addresses' tab, and scroll to find the filter you created.  When you do, click the corresponding 'delete' button on the right.