A tourist-focused store and card. I used the I amsterdam card. It gives you unlimited access to city public transportation (trams, some buses, metro, ferries, but not the NS trains since they are not local to Amsterdam) and activities (many museums, 1 canal boat tour, some others). It's cost-effective if you visit 1 museum or similar place per day, plus maybe 2-4 rides on some form of mass transit. If you plan to use it less frequently than that, it might still be convenient (even if it's not saving you money).
Be prepared for a few issues. The trams were not able to scan the app's QR code most of the time. Did not work at a metro station the one time I tried it. They let me on anyway.
The app's a bit slow. It takes maybe 10-20 seconds to load. If you're using public transit, you should open the app ahead of time so you don't hold up the bus or tram.
When booking museums, they need to scan both the ticket they email you as well as the app.
With the app, it does not start the timer until you activate the card, so buying the card a few days ahead of time is OK.
You can get a physical card instead of the app. It costs more, though I suspect it will not have the same scanning issues. The physical and digital forms are apparently not interchangeable. read more