LTI stands for Learning Tools Interoperability. These are codes which enable various resources to be more deeply embedded into Canvas. For the library, this generally means the content is being linked in the back end from the vendor so the links are more stable and often (but not always) are automatically authenticated for a user.
This guide will highlight the different LTIs for Library Resources that are in Canvas.
There are two places where LTIs can generally be found. One is when you are editing a page in Canvas. You will find the LTIs in a drop menu from the icon that looks like a power cord plug.
Some LTIs can also be added at the Module level as an external tool.