170 BPM means 170 beats every minute: one beat every 0.35 seconds (353 ms), or 2.83 beats a second. In classical terms it is Vivace, lively and fast (156–175 BPM).
You often hear tempos around 170 BPM in punk, ska, medium-up jazz and metal. The metronome above is already set to 170 BPM in 4/4: press Start, and change the time signature, accents, subdivisions or sound if your song needs it.