Development team leads are individuals who not only have a high level of proficiency in their specialised languages and tools (whether that's .NET Core, AngularJS, JavaScript or other languages), but are also able to make technical and architectural decisions that often seem difficult or unsolvable to others, based on a sound understanding of the problem and the pros and cons of alternative solutions. They can take complete ownership of delivery of tasks, projects or solutions, either individually or as lead of a sprint team.
A good team lead will be curious about all aspects of technology, and be an enthusiastic learner. They will enjoy challenges, be open and transparent about the problems they face, and will enjoy helping colleagues resolve their own problems without judgement.
Additionally, a team lead is able to manage a team of developers to bring the best out of them and raise their overall performance. They will also constantly bring knowledge and experience of new ideas, solutions and technologies into the workflow.