They are very similar. Consider this sentence: "There was a package on the floor. I picked it up, lifted it, and put it on a shelf." When I read "I picked it up," my mental image is of somebody bending over, grabbing the package, and taking it off the floor. The idea behind "picked up" is that the package was on the floor, now it is off the floor. When I read "I lifted it," my mental image is that somebody raises the package so that it is higher than it was. It was near the floor, now it is up high. The emphasis is on "higher." (Of course, "to pick up" is also a phrasal verb meaning "to drive a car, meet somebody, and take them somewhere.")

We can use them in two contexts. In the first, it means basically to elevate something from the ground, like a box or something: 1.I picked up the box. 2.I lifted the box However, we tend to use it more for transport. Pick up means more to collect somebody. Lift is a noun when you give someone a ride: 1. I will pick you up at the station and give you a lift home. 2. Can you pick me up at the airport and give me a lift to the meeting.

Generally, and in this context, the phrasal verb "pick up" refers to something small. The word "lift" is less specific and may refer to a heavier object.

Both of them can be used to mean "raise" or "elevate" something, but "pick up" usually means to "lift" something that is sitting on the ground or another flat surface... Also, "lift" is used with heavy objects whereas "pick up" is not (i.e. you lift weights at the gym but do not pick them up).