What are vendor or web browser prefixes?

CSS browser or vendor prefixes are nothing but a means through which the makers of web browsers (vendors as they’re known) add support for the latest CSS features, for an experimentation and testing period.
These browser prefixes are basically used for addition of new features, which may or may not be a part of the formal specifications. Furthermore, they’re used for implementation of new features in a specification which hasn’t yet been finalized.

Some of the CSS browser prefixes are as follows:
- Safari: -webkit-
- Chrome: -webkit-
- Internet Explorer: -ms-
- Opera: -o-
- Firefox: -moz-
- Android: -webkit-
- iOS: -webkit-

In majority of cases, one needs to simply take a standard CSS property and add the prefixes listed above for every browser, in order to use an advanced level CSS style property. For instance, for adding a CSS 3 transition to the document, you’ll have to make use of the transition property in the following manner, with each one of the browser or vendor prefixes detailed above:
-o-transition: all 4s ease;
-webkit-transition: all 4s ease;
-ms-transition: all 4s ease;
-moz-transition: all 4s ease;
transition: all 4s ease;

However, please remember that a CSS with the prefixed version of different properties isn’t the same as one with standard properties. For instance, you’ll need to make use of the linear-gradient property for creating a CSS gradient. Opera, Firefox and recent versions of Safari and Google Chrome use that property with an appropriate prefix. However, talking about the earlier versions of Safari and Google Chrome, they used to use the –webkit-gradient prefix property. In addition, Mozilla Firefox uses values that are different than the standard ones. Hope you get the drift!
You can easily make use of a tool called Prefixr to add all such vendor or browser prefixes automatically to your style sheet. This operation can either be carried out selectively or on the entire style sheet in one single go. Furthermore, as there’s a Prefixr API available, this service can even be used from inside different code editors.