What happens in service in a synagogue?

Answer 1

they pray and talk to god

Answer 2

Someone who does not know much about religion will see the same thing in synagogues and churches: People congregate, pray, sing songs, pray some more, and sing some more. There are elaborate rituals, including parades up and down the aisles, and ritual gestures.

Someone knowing more, will notice that synagogue services include lots of Hebrew, in much the way that Catholic services used to contain lots of Latin. They'll also notice that, in addition to communal singing, there is quite a bit of liturgical chant (again, this can be compared with traditional Catholic practice), and like Catholic and Anglican practice, the service follows a set text from a prayerbook instead of being more free-form.

A big feature of morning services on the Sabbath, as well as Monday and Thursday, is a reading from the scroll of the Torah. A reader knowing the liturgical chant for the Torah will do the reading while members from the congregation are called up to say blessings before and after each section of the reading.

Something else an observer might notice is a lack of hymnals. Reform Jews have published hymnals, but they are rare in synagogues. Most congregations (regardless of the stream of Judaism) sing to melodies that aren't written down in anyone's prayerbook but are passed down orally. As a result, two nearby congregations might belong to the same stream of Judaism, use the same prayerbook and yet use entirely different melodies to many of the songs.