Heroku is a cloud application platform from Salesforce for deploying, managing, and scaling apps. Code is pushed with git and runs in managed containers, so teams focus on the app instead of infrastructure.

Managed runtime - apps run in dynos with instant scaling, fast rollback, and app metrics.
Managed data services - PostgreSQL, Key-Value Store (Redis), and Kafka with one-click provisioning.
Developer workflow - GitHub integration with review apps, Heroku Flow for continuous delivery, and buildpacks for many languages.
Languages - Node.js, Ruby, Java, PHP, Python, Go, Scala, Clojure, and .NET, plus community buildpacks.
AI building blocks - managed inference and agents, MCP hosting, and vector search on Postgres.
Ecosystem - an Elements marketplace of add-ons, integrations, and buttons.
Enterprise - Private Spaces, Shield compliance, SSO, Heroku Connect to Salesforce, and team administration.

It is used by startups, agencies, and enterprises deploying web apps and APIs without managing servers.