7/4 has seven beats in each bar, and each beat is a quarter note (that is what the lower number means). In practice it is felt as two groups of uneven length (4+3). You will hear it in progressive rock and some folk and film music, usually felt as 4+3.
The metronome above is set to 7/4 with the beats grouped 4+3: an accent on beat 1 and a medium accent at the start of each group. The tempo counts quarter notes. Tap any beat to change its accent.