I am going to visit Disneyland, Anaheim, CA.I visited Disneyland website. I want to buy Theme park ticket. But I am confused as there is no clear definition which are include in this ticket? I also found out Tom Sawyer Island, which is one of the most visited place after Disneyland. Is the theme park ticket also include Tom Sawyer island? I am sharing a screenshot here. There are some palaces in screenshot marked in red. I want to know that , are they individual tourist sports or they cover Disneyland theme park ticket?
Disneyland Resort in Anaheim contains two theme parks (they're located next to each other on the same property): Disneyland Park and California Adventure, plus a couple of hotels and an unticketed shopping area called Downtown Disney. Disneyland Park is the classic, iconic Disneyland, while California Adventure is a newer California-themed area.
When you buy admission tickets, you can buy single park tickets, which grant admission to one park per day (if you buy a 2-day ticket, you can visit a different park on different days or the same park both days) or pay more for "park hopper" tickets, which allow you to go between parks on the same day.
Tom Sawyer Island (also other things you've circled like the Haunted Mansion and the Pirates of the Carribean ride) is an attraction inside of Disneyland Park. Rides and park attractions—excluding things like parking fees, special tours, food and drinks, souvenirs, etc...—do not require additional tickets and are included with your admission ticket.
The Disneyland website has a list of attractions, which you can filter by park and type. There are also many blogs and web sites that go into (too much) detail on planning Disney trips. This page from Mouse Hacking has a good overview of the basics, including the details of the FastPass and MaxPass systems, with links to many more resources.