The finite type invariant concept for knots was introduced in the 90's in order to classify knot invariants, with the work of Vassiliev, Goussarov and Bar-Natan, shortly after the birth of numerous quantum knot invariants. This very useful concept was extended to 3-manifold invariants by Ohtsuki.These introductory lectures show how to define finite type invariants of links and 3manifolds by counting graph configurations in 3-manifolds, following ideas of Witten and Kontsevich.The linking number is the simplest finite type invariant for 2-component links. It is defined in many equivalent ways in the first section. As an important example, we present it as the algebraic intersection of a torus and a 4-chain called a propagator in a configuration space.In the second section, we introduce the simplest finite type 3-manifold invariant, which is the Casson invariant (or the Θ-invariant) of integer homology 3-spheres. It is defined as the algebraic intersection of three propagators in the same two-point configuration space.In the third section, we explain the general notion of finite type invariants and introduce relevant spaces of Feynman Jacobi diagrams.In Sections 4 and 5, we sketch an original construction based on configuration space integrals of universal finite type invariants for links in rational homology 3-spheres and we state open problems. Our construction generalizes the known constructions for links in R 3 and for rational homology 3-spheres, and it makes them more flexible.In Section 6, we present the needed properties of parallelizations of 3-manifolds and associated Pontrjagin classes, in details.