Amphenol in-line 1/4" TS jack connector

Commonly known as a 1/4 inch jack, phono/phone jack.  There are two types - TS (Tip/Sleeve) which is two pole for unbalanced and mono connections such as from a guitar or old telephone switchboards (which is where the term phone jack originates), and the three pole TRS (Tip/Ring/Sleeve) used for balanced and stereo connections (eg balanced output from mixer, stereo headphones)