- Ok water is one of the 5 basic elements and from what I've seen the most versatile of the 5.
Weaknesses-
Well water has been shown to be weak against earth style jutsu because earth just absorbs moisture and can also withstand impacts from water jutsu. Water also can be weak against raiton at times, if someone uses a body of water as a conductor for the raiton it could be dangerous.
Strengths-
Suiton is and always has been the ideal defense for fire techniques. Water techniques easily overcome fire techniques but can also overcome some raiton techniques thus making the water more deadly.
village that uses it most/Users etc.-
Kiri seems to use it most, most likely due to them living in an environment that consists of a lot of water. I believe the majority of kiri shinobi show has used some type of water skill.
Users: Tobirama senju was noted to be the greatest water user, being able to use large scale water jutsu with no water source. Another superb water user is Kisame Hoshigaki, who is actually shark like in appearance and in my opinion is the greatest water user in history.
Ways it can be made: well as I noted above, water jutsu can be made out of thin air, or the moisture in the air. But most users need a body of water to make their jutsu. It can also be released in a mist form used for skilled, silent killing or just taking your opponents view away.