Ludwig Wittgenstein's "Tractatus Logico-Philosophicus" is a seminal work in philosophical logic and the philosophy of language. Both the introduction and preface of this work set crucial context and aims that guide the reader into the complex ideas presented in the main text.

Introduction
The introduction to the "Tractatus Logico-Philosophicus" is typically not written by Wittgenstein himself but is provided by Bertrand Russell, a significant figure in analytic philosophy and a mentor to Wittgenstein. In the introduction, Russell outlines the main objectives of Wittgenstein's work and its revolutionary nature within the realms of logic and philosophy. He discusses the importance of Wittgenstein's ideas about the structure of language and its relationship to the world, noting how these ideas relate to and differ from contemporary and traditional philosophical thoughts. Russell emphasizes the radical conclusion that Wittgenstein reaches, which is that most traditional philosophy consists of nonsensical pseudo-propositions due to its misuse of language.

Preface
Wittgenstein himself wrote the preface, where he briefly explains his philosophical investigation's origins and intent. He notes that the book's main purpose is to draw a limit to the expression of thoughts, and by doing so, also to the thoughts themselves. Wittgenstein suggests that in elucidating the propositions and logic that can be meaningfully discussed, one can also identify what cannot be said, which he associates with the mystical or ethereal aspects of human life. He expresses a hope that by clarifying the propositions that can be expressed meaningfully, all other nonsensical propositions will disappear, thereby solving philosophical problems rather than just answering them. Wittgenstein acknowledges the difficulty and abstractness of his work and notes that he has achieved his purpose if he brings some clarity to those who think similarly about these problems.

Both the introduction by Russell and the preface by Wittgenstein set the stage for a dense exploration of philosophical logic, aiming to clarify the limits of language and thought. They suggest that understanding these limits can resolve many traditional philosophical dilemmas by showing them to be based on misunderstandings about the logical structure of language.