Altmetrics measure impact in ways traditional citation counts and impact factors don't. This can include social media buzz, usage statistics, follower counts, and more. They can also assess the impact of other research outputs like data sets, software, posters and presentations, and videos. They can also provide information on the breadth and composition of your audience.
Altmetrics aren't meant to replace traditional measures, but complement them. They can help gauge the immediate impact of your work, before enough time has passed for formal citations. They are measures of attention, not necessarily quality.
Examples of Altmetrics
Context is important! Rather than just listing a bunch of statistics on your CV or tenure dossier, explain what they mean. Provide a qualitative explanation to back up your quantitative data.
Include metrics that document the types of impact you want to showcase, rather than including every possible statistic you can find.
Being selective with your statistics will help them make more impact, instead of overwhelming your audience with numbers.