The envelope

Everything that ever changes the Stellar ledger travels inside one shape — a transaction envelope:

• Source account — who is acting (and paying the fee).
• Sequence number — this account's transaction counter.
• Fee — what you bid to be included.
• Operations — the actual verbs (1 to 100 of them).
• Signatures — proof the source (and anyone else required) agreed.

There is no second shape. A payment, a token issuance, a smart-contract call, a trade on the DEX — all of them are this envelope with different verbs inside. Learn it once and every explorer page and SDK call on Stellar becomes readable at the same moment.