It contains wallet-specific settings, transaction & address history, labels, contacts, invoices, master (private/public) keys, and others data depending on the wallet type.
But for other data like labels, contacts and active invoices;
you'll need to copy "wallet_1" file to computer2's 'wallets' folder inside electrum datadir and open it via Electrum's "File->Open" menu.
There's also a "LabelSync" plugin if you want to backup your labels (encrypted) on a server to be restored when you restore your wallet via seed phrase.
Both clients should have the plugin enabled (Tools->Plugins) for it to apply.