Trello is known for it's signature use of kanban boards, lists and cards which provides a visual way to organize tasks. Because of it's simplicity, it's one of the most well-known task/project management tools on the market.
Trello is what we'd consider a "project management tool for beginners" due to it's gentle learning curve. It might be useful if you are just wanting a free tool that can help quickly help you start to visualize your process. But you'll likely outgrow it very quickly.
While Trello was the first app to visualize your projects in a kanban view, this feature is now widely adopted among almost every project management tool on the market. We used Trello here at Efficient App for years, before ultimately switching to Asana, when they too added kanban functionality, as we felt that Trello sort of got a bit stuck, while their competitors were evolving and working to further innovate in the project management space.
Because Trello's stagnation, it's not an alternative we'd highly recommend, simply because there are much more innovative tools on the market now (most of which are listed in this article).
Airtable is a database (you can use it as a replacement to Google Sheets for example). Because of it's versatility, some folks get excited about the idea of what Airtable can do since it is almost endlessly customizable.
Because of Airtable's flexibility, you are technically able to use it for task management or project management but in terms of functionality, it doesn't compete with the likes of Motion, Sunsama, Akiflow, Asana, Monday, ClickUp, etc.
Airtable won't work well as a project management for complex projects, it will easily become confusing to navigate. While Airtable might work for very basic project management if you're a super small team (1-3), the time you spend setting it up and figuring out "how to best use it" is better spent on actually getting your work done. With that, using another alternative on this list that is more opinionated in terms of project management and has more features pre-built for managing projects, will be a much better choice long-term.
Airtable is not a traditional CRM software, it's first and foremost a database (you can use it as a replacement to Google Sheets for example). Just like some people use Google Sheets as a CRM, you can also "technically" use Airtable as a CRM—though it's not something we ever recommend.
The reason is because Airtable lacks the main features of a CRM, like ingesting all your teams emails in one place. Further, because there is unlimited flexibility with Airtable, you can get stuck spending dozens, if not hundreds of hours, configuring Airtable to function as a CRM. And more likely than not, the tool will lack proper adoption as there are little guardrails when using the tool for CRM purposes and everyone can kind of use it "how they want".
In general, while Airtable tries to position itself as a contender in the CRM space due to it's customization abilities, it's the main reason why we advise teams not to go down this path. It will likely lead to overwhelm and sunken time that could have gone into setting up a proper CRM that will scale with time.
If you're tempted to use Airtable as a CRM, we'd recommend folk instead as it will still give you a similar database like structure, all while providing CRM features at the core.