This device is used to store your BTC right but just a question what will happen if I lost it? will I still be able to recover my coins? How is it being updated to the block chain?
If you lost it... you use your 24 word seed mnemonic to restore another replacement HW wallet, or into a wallet that supports BIP39 seeds, like Electrum, or you use a tool like the BIP39 Mnemonic Code Converter (https://iancoleman.github.io/bip39/) to generate all the addresses/private keys that belong to your 24 word seed mnemonic and you import/sweep the required private keys into the wallet of your choosing.The wallet itself is not "updated to the block chain". It is simply a keystore for you private keys. The actual transaction type information is generally held in a software wallet on your PC/Phone in what is effectively a "watching only" wallet (ie. it has no private keys stored in it). You then use the software wallet in conjuction with your hardware wallet to sign transactions/messages when required (ie. software wallet sends unsigned transaction to hardware wallet, you confirm all the details and click "ok", hardware wallet signs the transaction and sends it back to software wallet for broadcast etc)
Planning to buy one but I really have a lot of questions about it. 
Then I suggest you head over to either Trezor.io or legderwallet.com and start reading their FAQs etc:http://doc.satoshilabs.com/trezor-faq/index.html
https://ledger.zendesk.com/hc/en-us/categories/115000820045-GENERAL-OVERVIEW
Both of those sites have pretty comprehensive documentation explaining all about hardware wallets and how they work.
