Domain modeling is the process of creating a conceptual model of the domain that the software system will address. It is an activity that takes place during the design phase of software development, where a team of software engineers and domain experts work together to identify the key concepts, entities, and rules that define the problem domain. The resulting model is a set of abstractions that represent the domain in a way that is understandable by both technical and non-technical stakeholders. The goal of domain modeling is to create a common language that everyone involved in the project can use to communicate effectively. This helps ensure that the software solution being developed meets the needs of the business or organization it is intended to serve. Domain modeling is a key component of Domain-Driven Design (DDD), a software development methodology that emphasizes the importance of understanding the problem domain in order to create effective software solutions.

There are several lightweight and effective methods to perform domain modeling, including but not restricted to:

1. EventStorming: This is a collaborative workshop format that allows domain experts, software developers, and other stakeholders to explore and understand complex business domains. In an event storming session, participants use sticky notes and markers to visualize domain events, commands, and aggregates, and identify business rules and invariants.
2. User Story Mapping: User story mapping is a technique for organizing and prioritizing user stories by grouping them into high-level categories, and then breaking them down into smaller tasks. This method helps teams to understand the user’s journey and the different tasks required to support that journey.
3. Domain Storytelling: This is a method of collaboratively exploring and sharing knowledge about complex business domains through storytelling. In a domain storytelling session, domain experts share stories about different aspects of the domain, and these stories are used to identify concepts, relationships, and business rules.
4. Example Mapping: This is a technique for refining user stories by breaking them down into concrete examples. In an example mapping session, participants use concrete examples to identify different scenarios that can occur when a user interacts with the system, and these scenarios are used to drive the development of the domain model.

These lightweight methods are highly effective for domain modeling because they encourage collaboration, focus on concrete examples, and allow teams to explore complex business domains in an iterative and incremental manner. They also help to align the understanding of domain experts and technical teams, which is critical for building successful software systems.