All transactions are stored in a database called a "block chain". Transactions are grouped into "blocks" and the blocks are linked together in a sequence (the "chain"). In order for a miner to add another block of transactions to the chain, all miners must agree that the block and the transactions it contains are valid.

If miners disagree on the validity of a block then there will be a "fork" where one group of miners adds the block to the block chain and the others do not. The result is that the chain diverges as the two groups of miners continue adding blocks to the chain that they think is valid. Since they cannot agree on that one block, there will always be two chains.

Bitcoin Gold and Bitcoin Cash (and Segwit2x) are intentional forks. In an intentional fork, a group believes they can improve Bitcoin by making a change, but the change is not compatible with the previous rules.

I am surprised assuming that you are a newbie as you are saying and you do not know how to sell without card. May I know how did you bought the btc without Pan card?  In case you had got from someone else and want to sell then only thing is that you can ask here if anyone wants to sell and then do a escrow deal.

In the context of bitcoin and cryptocurrency.

Fork has 2 main meanings.

First meaning is relating to code development and is shared with all software projects.

The code base of bitcoin can be forked to form the basis for the development of a new project. This has happened many times.

Second meaning specifically concerns blockchain based cryptocurrencies.

The blockchain is a data structure where each block is linked together with a cryptographic hashing function that allows the younger block to inherit a digital fingerprint of the data in its parent block.
The fork occurs at the tip of the blockchain where there are 2 child blocks that are created simultaneously, subsequently propagated throughout the network, creating a conflict of consensus.
Part of the network will then have a different copy of the blockchain than the other, and the network will continue creating new blocks until the chain with the most blocks is finally accepted by the entire network.

Such is the case with any fork that occurs where there isnt an intent to change the underlying policy of the network.

The other type of blockchain fork is the policy changin type of fork.

In a soft fork like segwit bip141 there is a policy change but the forked blockchain continues to run in parallel because it is backwards compatible. participants are free to move their bitcoins back and forth between segwit enabled and legacy addresses.

In the hard fork as with bitcoincash, There is a policy change that does not permit backwards compatibility. The tail of the blockchain is cloned so that participants of the original network will have an equivalent balance on the cloned chain. each version of the blockchain then eliminates their respective policy violating fork and continues to build itself as 2 separate blockchains.

All transactions are stored in a database called a "block chain". Transactions are grouped into "blocks" and the blocks are linked together in a sequence (the "chain"). In order for a miner to add another block of transactions to the chain, all miners must agree that the block and the transactions it contains are valid.

If miners disagree on the validity of a block then there will be a "fork" where one group of miners adds the block to the block chain and the others do not. The result is that the chain diverges as the two groups of miners continue adding blocks to the chain that they think is valid. Since they cannot agree on that one block, there will always be two chains.

Bitcoin Gold and Bitcoin Cash (and Segwit2x) are intentional forks. In an intentional fork, a group believes they can improve Bitcoin by making a change, but the change is not compatible with the previous rules.