While different companies have different definitions of positions (anecdotally, my employer uses a total of 8 levels instead of the customary 3), there is a fairly common consensus about what it means to be a junior/medior/senior.
- Juniors can do their tasks, albeit with some help or guidance
- Mediors can do their tasks
- Seniors can do their tasks and have time for either assisting juniors or further improving their output quality
This isn't a hard line, of course. Some difficult tasks will have mediors or seniors needing to cooperate as well - asking for help doesn't immediately downgrade them to a junior position. The bullet points are more of a guideline for what you can expect during day-to-day tasks.
There are of course other considerations as well. You'll generally expect a senior to know more than a medior; but whether that is counted using the variety of tech stacks a dev knows, the depth of knowledge on individual tech stacks, or ancillary project managing abilities; is up to the company to define.
The answer is always the same, that I doing great, picking up things fast, and willing to learn new things.
This feedback isn't indicative of what level you're at. It's indication of progress on that ladder. In other words, they're saying that you are making progress, and there are no particular things you're doing that are impeding your progress.
Medior and senior level come with time. While it usually aligns with how long you've been doing the job, this is not a hard and fast rule. Some developers may be actual wunderkinder who shoot up the ladder, and others may evolve more slowly or experience a slower progress. This can be due to either aptitude, bad guidance from others, lack of motivation (either from yourself or others, personal life intervening in their career experience, ...
In short, there is no hardset track to define your progression from junior to medior to senior. It's a matter of how the company defines those levels, and how they observe your handling of the tasks that were assigned to you.