Hanami means literally "looking at the flowers". And that's also how the japanese call the sort of picnics that they organise specifically during the cherry blossom "sakura" season.
They usually gather with their classmates, colleagues, friends or family to have drinks and food under the "rain" of sakura petals.
Tama area is the name of the western part of Tokyo Metropolis. It consists of 26 cities, 3 towns and a village. A lot of people (about 4 milion) live in a eastern half part of the area. However, there are many mountains in the western part of Tama area, and there are very little flat land. Many hiking spots are in the western area, so you can enjoy walking on the trail, camping, and so on. If you see the beautiful mountain scene, you may not believe this is also in Tokyo.