Your question refers to the use of the phrase "secure path" in slide 13 of a talk about Simple Authentication Protocols (or the same/similar slides in several other talks or courses). This context states that "Authentication on a stand-alone computer is relatively simple" but that "attacks on authentication software, keystroke logging, etc., can be issues".
In this context "secure path" refers to the path which leads to the final authentication result, i.e. entering the authentication credentials and validating these credentials. While there can be attacks which affect the security of this path, like key loggers or bugs/backdoors in the authentication software, this path can still be considered sufficiently secure, especially compared to authentication over a network which is the next point on the slide. Thus, "secure path" is meant to be read as not fully secure (that's why it was put in quotes) but comparatively secure in contrast to authentication over a network.