Yes, Prahara is one type of time measure. The full day is divided into eight parts.
According to Srimad Bhagvata Purana:
लघूनि वै समाम्नाता दश पञ्च च नाडिका ।
ते द्वे मुहूर्तः प्रहरः
षड्यामः सप्त वा नृणाम् ॥SB 3.11.8 ॥ Page 279
laghūni vai samāmnātā daśa pañca ca nāḍikā
te dve muhūrtaḥ
praharaḥ ṣaḍ yāmaḥ sapta vā nṛṇām
Six or seven Nadikas make one Prahara of men. It is also called Yama.
यामाश्चत्वारश्चत्वारो मर्त्यानामहनी उभे।
पक्षः पञ्चदशाहानि शुक्लः कृष्णश्च मानद ॥ 3.11.10||
It is calculated that there are four praharas, which are also called yāmas, in the day and four in the night of the human being. Similarly, fifteen days and nights are a fortnight, and there are two fortnights, white and black, in a month
We can read more about the measurement of time uptil Prahara in verse no. 5-8 of same chapter of Bhagavad Purana.
I recommend to refer Panchanga to have complete and reliable information about Prahara and Muhurta.
The names of four Praharas of the Day are as follows:
- pUrvAnha (पूर्वान्ह)
- madhyAnha (मध्यान्ह)
- aparAnha (अपरान्ह)
- sayAnha or sAyaMkAla (सयान्ह or सायंकाल)
And the Night is considered to be consisting the time of three prahara called
- triyAmA (त्रियामा) and remaining
- uShA (उषा)
Though some narrates the the four Praharas of Night as follows (but I have not find reliable source to this):
- pradoSha (प्रदोष)
- triyAmA (त्रियामा)
- uShA (उषा)
Talking about significance of each Prahara, it is believed that there is a specific time to sing particular Raga i.e Some ragas are prescribed to be performed at a particular prahara. And there is also significance of performing worship in specified Prahara.
: Gauravshali Bhartiya Kalaganana, page 33.