In a previous scene, Capulet and Paris agreed that Paris should marry Juliet on Thursday at St. Peter's Church. However, it is the groom's job to make the arrangements with the priest, which is what he was doing at Friar Lawrence's cell. Romeo was the one to make arrangements with Friar Lawrence about his wedding to Juliet, as you will remember.
It's not a jail cell. The rooms that monks live in are often called cells, because they are small and sparse. Friar Lawrence is not only a priest, but a Franciscan friar, which is a kind of monk.
to discus the wedding plans made for him and Juliet
They are to meet there in order to get married.
to help marry him and Juliet
because he is a chloroplast
Friar's Cell
Romeo asks friar Laurence to marry him and Juliet in secret
Friar Laurence is Romeo's confidant, and the play suggests Romeo has known him since he was very young as it implies that the Friar is a religious leader. Friar Laurence is to Romeo; what the nurse is to Juliet.
His cell is the place where he lives. A monk's cell isn't a very fancy room, any more than a jail cell is.
To confess her sins and be absolved.
Friar's Cell
Friar Lawrence married Romeo and Juliet in his cell.
In Friar Laurence's cell
Romeo hides in Friar Laurence's cell after Tybalt's death.
Friar Laurence was created in 1597.
He was to take Juliet to his cell and await for Romeo to appear.
nurse
Twice in the play Juliet is allowed to visit Friar Lawrence's cell on the pretext of going to confession. One of those times is to marry Romeo. It would appear that this is the only excuse she can use to get out of the house.
Romeo asks friar Laurence to marry him and Juliet in secret
in his cell or other wise known as the church
The first time when she arrives at his cell, Romeo is there ready to get married to her. The second time Paris is there, making arrangements to get married to her. There's a kind of parallelism there.
Friar Laurence belongs to the Franciscan religious order.