TMF can also stand for the LinuxTools project's Tracing and Monitoring Framework.
The Textual Modeling Framework (TMF) is an umbrella project under the Eclipse Modeling Project (EMP). It hosts two different framework for implementation of textual syntax for EMF models (aka Ecore models).
TCS (Textual Concrete Syntax) comes from GMT. With TCS one annotates concrete syntax information to existing ecore models. The editor is not generated but interpreted.
Xtext was previously part of the openArchitectureWare framework, but is now developed under Eclipse Modeling.
Xtext is a framework for development of programming languages and domain specific languages (DSLs). Just describe your very own DSL using Xtext's simple EBNF grammar language and the generator will create a parser, an AST-meta model (implemented in EMF) as well as a full-featured Eclipse text editor from that.
The Framework integrates with technology from Eclipse Modeling such as EMF, GMF, M2T and parts of EMFT. Development with Xtext is optimized for short turn-arounds, so that adding new features to an existing DSL is a matter of minutes. Still sophisticated programming languages can be implemented.
It is intended that at some point there will be only one framework instead of two. Requirements and thoughts can be discussed here