I am assuming you are referring to on the browser, and assuming that browser is Chrome? The simplest way, in the Chrome Browser, to remove/delete tabs is to do one of the following.
To close each tab individually (and not close all of them)...
1. Press the "Tab Number" near the top right, or in Android 5.0 and higher (Lollipop and Marshmallow), tap on the "Square Button" in the lower right corner.
2. Then just "swipe" away each tab individually.
To close all the tabs in the browser, there are two ways to do this...
First way...
1. Tap the "three-dots" aka "Menu" from inside the browser.
2. Now choose "Settings".
3. Then choose the option "Close All Tabs".
Second way...
1. Tap the "three-dots" aka "Menu" from inside the browser...