CLICK.

• click
• 1 [intransitive and transitive] to make a short hard sound, or make something produce this sound:
• The door clicked shut behind me.
• Mother clicked her tongue (=made a short sound to show disapproval) and sighed.
• Edmund clicked his fingers (=made a short sound to get someone's attention) for John to follow him.
• Vogel clicked his heels (=hit the heels of his shoes together) and bowed.
• Twist the lever and the gears click into place.
• 2 [intransitive and transitive] to press a button on a computermouse to choose something from the screen that you want the computer to do, or to press a button on a remote control:
• Choose the image you want by clicking twice.
• click on
• Children can click on a sentence to hear it read aloud.
• 3 [intransitive] informal to suddenly understand or realize something:
• It's hard work, but one day it will just click.
• I thought, 'What is he doing?' and then suddenly it all clicked into place(=I understood how all the events related to each other).
• 4 [intransitive] informal if two people click, they like, understand, and agree with each other:
• They clicked straight away.
• 5 [intransitive] informal to happen in a good or successful way, especially because people are working together well:
• If everything clicks, we should have a good season.
• Definition from the Longman Dictionary of Contemporary English 
• Advanced Learner's Dictionary.