'Blossom' means flower. As I said, it is in bud now so it will flower any time soon. After the flowering/blossoming comes the seed. The sequence is Bud, Flower/Blossom, Fruit/Seed. As carrieb said, you will notice the delicious scent of the flowers and probably the sound of bees which love Linden blossom. Makes great honey.

Cottonwood. Wonderful trees, will live 100 years and counting in this area. The big drawback is that the female trees will release cotton in mid summer which can be a real pain from a large tree or a lot of trees. They will grow quickly, and can get pretty big, 6' or more in diameter in an old (40-50+ yrs) tree. Old trees often get some wood rot and can lose large limbs in high winds, and if you let a multitrunked tree grow, you will sooner or later find one of the trunks laying on the house or car or pet, or if nothing else is nearby, the ground. They are really great trees, but not the best to have next to a house unless you just want them for 20 years or so to have a fast growing shade tree while something slower can grow up. Also, if you are approaching retirement and hate your kids (who want your house), they are great trees to plant--by the time your kids get the house in 30 or 40 years, you will have enjoyed it and the tree will be their responsibility to take out!

It is a pear tree. Notice the shape of the fruit on the upper left. Looks like an unside down pear. Once the fruit gets some weight to it, the fruit will bend down. Here is a link that might be useful:

A member of the Solanaceae. A location would be very helpful as would pictures of the flowers when they open.