the.com/title track

means The song on an album that shares the album's name, usually signaling it's the thematic or commercial centerpiece.

from A straightforward compound of 'title' (from Latin titulus, an inscription or label) and 'track' (music industry slang for a single recorded song, borrowed from the physical grooves cut into vinyl records). The phrase itself is a 20th-century music-industry coinage, rising with the album era, when a record needed a name and one song was chosen — sometimes by merit, sometimes by marketing — to lend it that name.