It's quite hard to define the tech lead role in a short post. But, here it goes.
Tech lead is a role, not a title. Any software engineer can become the tech lead. And with the part, others will look up to this leader.
The lead is the team liaison. The role shepherds change. They focus on the future state. The rapid response. The pivots from management.
Tech leads play the role of mentor and sponsor to others. They setup code reviews in a collaborative way. They handle discourse. They partner with the product on feasibility, on a roadmap, priority, and estimations.
They are accountable for the developer's experience. The technical debt and engineering velocity. The tooling and onboarding friction. The testing, product domain, and holding philosophies to approaches.
They write down the philosophies so that decisions are apparent. They are the guide with respect — a leader who delegates as well as leads by example.
Being a tech lead can be a challenge. Managers pressure them to do the impossible. Priorities come to them in all directions. Their impact is good or bad, whether the team is pathological or generative.
The lead is there to see the team succeed, to deliver. Without internal injuries, with an orchestra of collaborative engineers rising.
The brutality of being a tech lead is the demand for the individual's technical and management capability. Even though companies have split these into two ladders, the role of tech lead has intractable attributes of both. It is impossible to separate.
The team can blaze a path in the lead's absence. Whereas the real drama happens in one's head, the pure emotion of the group occurs in front of the tech leads eyes. The lead follows through it and guides.
They lead with a myriad of soft skills jujitsu. With the technical tact unmatched. And if it all goes wrong, no worries. There are marketing opportunities.