There are several things you can do from the Lock Screen on your iPhone. One of those things is to search for certain things. This may be convenient for some, but a privacy problem for others. Here is what this entails.
Spotlight Search is enabled by default on the iPhone Lock Screen, along with Today View. This may be convenient for some users, but for others it’s either annoying, unnecessary, or a potential privacy breech as anyone who picks up the iPhone can see and search through your apps, calendar, and other personal data.
I have it turned off for privacy reasons. This article explains how this works and how to turn off lock screen search if you choose to do so.