Bilbo is pure of heart and, though he is small, was able to resist the power of the Ring - for a time. Eventually, it took a hold over him, and he had to pass it on to Frodo. -sam-is-my-hero-
In the Lord of the Rings, Bilbo Baggins steal the Ring of Sauron, which he made to rule over all the other rings. Bilbo later on than passes the ring on to Frodo Baggins, his youngest nephew, to destroy. This leads to the story, The Fellowship of the Ring.
Gollum guesses that Bilbo has found his magic ring.
The One Ring - the ring made covertly by Sauron to rule all the Rings of Power.
In chapter 5; Riddles in the dark; bilbo finds a ring.
Many people knew that the One Ring existed, but they didn't know that Bilbo had it, except for Gollum. Gandalf suspected that Bilbo had the ring, but he wasn't sure.
The ring that Bilbo found is known as the One Ring, and it was originally forged by the Dark Lord Sauron. Before Bilbo discovered it, the ring was lost by Sauron and later came into the possession of Gollum, who called it "my precious." Bilbo found the ring in Gollum's cave during his adventure in "The Hobbit," ultimately becoming its new owner.
Because Bilbo won it in his game of riddles with Gollum.
Bilbo said, talking to himself, "what have i got in my pocket?" (it was the Ring). Gollum thought it was a riddle and Bilbo decided to make it one. he gave Gollum three chances to guess and gollum lost after four. then gollum went "to get something" (it was the ring), and Bilbo thought he was abandoned and left with the ring on. Gollum thought Bilbo knew the way out and he wanted to follow him, realizing Bilbo had the ring. Bilbo saw Gollum racing towards the gate and followed him to safety.
Bilbo Baggins
it makes him invisible
After Bilbo puts on the Ring and turns invisible, Gollum cannot find him, and thinks he has made his way towards the exit. Gollum heads to the exit and Bilbo follows him.
Bilbo gives his cousin Frodo the One Ring after being hard pressed to do so by Gandalf. In fact, Bilbo almost drew his sword on Gandalf.