tissues are simpler than organs. Hence tissues are made up of a group of cells. for eg neurons the nerve cells grouped and make up nerve tissues. and those nerve tissues gather and form brain. while the nerve cells specialized to support the body make up nerve tissues and those tissues make up spinal cord.
So the differences are
tissues are simpler while organs are complex
tissues consist of group of cells while organs consist of group of tissues
tissues makes organs while organs make organ system
I hope my answer will satisfy you