This video will teach you the flap T sound /ɾ/. The sound symbol looks like the letter R but it is actually an alternative way of pronouncing the consonant sound /t/.
When speaking naturally, the voiceless plosive /t/ can change into a voiced short flap against the alveolar ridge (= the bump just behind your top teeth). The result is a new sound: /ɾ/, called the flap T, flapped T or simply flap or tap. It occurs mostly in the English spoken in North America, Australia and New Zealand.
In British English the voiceless /t/ does not usually change into a flap T. The flap T is therefore a prominent feature of an American pronunciation, and you will hear it often in films and TV series from the US. So, if you would like to give your English accent a bit of an American flavour, learn more about this sound in this video and start practising it.