After a report has been published you will want to ensure that the data in that report stays up-to-date. For reports that use DirectQuery data sources or Live Connections, your data will always be up-to-date without you needing to do anything (00:45). Reports that use imported data, though, will need to have the data behind them refreshed on a schedule (01:38).
If your report uses an on-premises data source then you will need to install a gateway (05:08). Setting up a gateway in Personal mode is suitable for scenarios where the gateway is run on a desktop PC (06:29); in most corporate scenarios you should set up your gateway in its normal mode (something that previously was called Enterprise mode, and is still often referred to as such) (07:40).