• F1 hybrids are the work of plant breeders. They are the first generation raised by cross-pollinating two different types of tomato. You can save your own seed from F1 fruit but when they grow the following season they won‘t necessarily turn out the same (be “true to type“). But open-pollinated tomatoes, such as heirloom varieties, are more stable and will look like their parents.
• Indeterminate varieties grow as tall vines. They keep growing and produce fruit until the first autumn frosts kill the plants off, whereas determinate or bush types are more compact with a strong central leader. They don‘t need as much staking but fruit for a shorter season.