Shepherds keeping watch
The reason why they were there looking after their sheep at night and what the sheep were going to be used for, is an interesting matter for discussion.
These men lived in the open looking after Sheep. Each shepherd knew each of their sheep by name and each sheep knew the voice of their shepherd. Flocks were approximately 10-20 sheep.
Unless these sheep were Temple sheep and that is a different story.
The shepherds found a newly born baby [Greek brephos].
Background Reading:
Luke 2:8-12 & 15-20
The Shepherds and the Angels
8 And there were shepherds living out in the fields nearby, keeping watch over their flocks at night.9 An angel of the Lord appeared to them, and the glory of the Lord shone around them, and they were terrified.10 But the angel said to them, "Do not be afraid. I bring you good news of great joy that will be for all the people.11 Today in the town of David a Savior has been born to you; he is Christ the Lord [The Messiah (Anointed) the Lord.]12 This will be a sign to you: You will find a baby wrapped in cloths and lying in a manger."
15 When the angels had left them and gone into heaven, the shepherds said to one another, "Let's go to Bethlehem and see this thing that has happened, which the Lord has told us about."
16 So they hurried off and found Mary and Joseph, and the baby, who was lying in the manger.17 When they had seen him, they spread the word concerning what had been told them about this child,18 and all who heard it were amazed at what the shepherds said to them.19 But Mary treasured up all these things and pondered them in her heart.
20 The shepherds returned, glorifying and praising God for all the things they had heard and seen, which were just as they had been told.