Each node of the network (miners and all other nodes that run Bitcoin client) has a copy of the ledger. Thus, the ledger is stored by the nodes (it is distributed in exactly this sense!). The ledger is periodically updated with new blocks of transactions being sent to the nodes. Hypothetically: If I am a miner and want to create a fork I can easily do it by creating a block and sending it to the network and the network will add it to the ledger. For example, for the chain A-B-C-D, I can add a block B2 to B, thereby creating a fork at node B. Of course, this block will most likely be orphaned because it is not the longest branch and the miner did it, say, for fun. Is my understanding right? If not, please point out what is not right.
You are correct, except that your block will be rejected or eventually forgotten by everyone else but you. Nodes typically only keep the blocks in the longest chain, though they may keep orphaned blocks for a little while in case they somehow becomes the longest chain.