This cartoon by Chappatte from the New York Times relates to the claims by Donald Trump via Twitter that Barack Obama tapped his Trump Tower phones during the presidential election. You can read Trump's tweets here.
The scene is the Oval Office. Donald Trump is at his desk, tapping furiously on his phone. We can assume that he's sending tweets or tweeting on Twitter. One of his aides comments to another (Kellyanne Conway?), "That's the sort of tapping I'm worried about."
The joke relies on a play on the word 'tap'. If you tap (or wire-tap) someone's phone, you connect a device to a telephone so that the conversation can be listened to secretly, or do so remotely. But the word 'tap' can also mean 'to touch lightly', for example when you tap on the screen of a mobile device in order to enter text or make something happen. The aide is worried because Trump routinely uses Twitter to attack his opponents, often without justification. For example, in this case, there is no evidence to support Trump's wire-tapping allegations, which one senior US intelligence official called 'just nonsense'.
• Obama Wiretap (Cagle.com cartoon collection)