Greetings to all members of BTCTalk forum, I'm new to this forum, but I have some basic knowledge about BTC in general. I hope that we'll all get along. I currently have miserable amount of BTC in my wallet, but I hope that will change from time to time. I write in my free time and I hope that my book will see the light soon. 
Anyways, I searched the forum, but couldn't really get the answer from it so I ask for people who know to answer me.
Question:
How can someone steal your wallet? I mean can they just grab it from a website or can they steal your wallet like they could steal your email and its password by keylogging, infecting with trojan and so on? And what happens if I for e.g. crate a backup of my wallet that has 0.01BTC and someone steals it from me and spends everything from it and I back it up after a day or two?
Thank you all in advance for taking your time to read my topic! 
To simplify, your funds aren't actually kept inside a wallet. It's kept as part of the bitcoin network.
As such, if anyone have your private key, they can steal all the contents in your wallet (send all your btc to themselves)
If you're using an online wallet like coinbase (who maintains your bitcoin address and the private key for that address), if they have your user name and password, they can steal everything in your wallet.
