Hijrat means migration. Hijrat refers to migration of muslims from Mecca to Medina and it is from this date that the muslims mark their calendar.
When the muslims fled to Medina, Muhammed (peace be upon him) I believe was the second last muslim to leave Mecca. Ali (may Allah be pleased with him) was the last. Abu Bakr (may Allah be pleased with him) accompanied the holy prohet to his journey.

During the start of their journey , Quraish (the meccan pagans) announced a reward for the head of the holy prophet (peace be upon him) and went to catch the holy prophet themselves (before he could reach Medina).

Muhammed (pece be upon him) was still well within a distance where he could be caught up by the Meccans.

It is said that he and Abu Bakr hid themselevs in a cave for 3 days. During this time the Meccans gave up on their persuit to find Muhammed (peace be upon him).

Kindly name this cave and as per Islamic traditions tell the reason why the Quraish were were not able to find Muhammed (peace be upon him).

Thaur.The enemies found a trail up to the mountain where Muhammad (pbuh) and Abu Bakr were hiding. When they came to the cave they found a bird's nest and spider's web at the entrance of the cave and thought that no one could be inside. So the enemies left without looking in the cave.

Answer is right. Good answer. Normally a muslim is taught as a child in school about the spiders web. But when one reads these stories (himself), one also sees the birds nest as another reason for Meccans not checking the inside of the Cave.

It is also one of the reason that as a child, one took special care for not harming a spider lol.