You can have accounts online and offline. Online accounts are accounts that have tokens and have generated a participation key, the account has been taken online on a specific node(which could be your own) using the generated participation key and is now participating in consensus. Offline accounts are accounts with tokens but have not taken the account online on a specific node. If a node has one or more accounts online then it is a participating node.
From the FAQ
While anyone can run a participation node, not all users will have the technical ability to participate in the consensus protocol. For users who are not able to run a participation node, the Algorand blockchain offers an offline mode. When a user declares themselves offline, their account’s stake is not taken into consideration for the sortition process. This allows any user to have a stake in Algorand without requiring them to operate a participation node.
Currently, the system treats all users equally. In the future, the Algorand Foundation may propose an upgrade to increase the rewards given to online users—incentivizing them for their participation in the cryptographic sortition protocol—and decrease the rewards given to offline users.