It tells you when to plant it, how deep, and roughly how long it takes for the plant to grow. However, this type of packet is better:
(Notice both packets have dates on the side, that's the year that the seeds were packed for. I have some that are several years old that still work, just know that the closer you are to the current year, the more likely it is that all seeds will sprout.)
This one shows the zones in the U.S. (we are zone 7 here, and most things will grow, surprisingly) It tells you how long before the seeds sprout (germinate), and how long before you'll actually get something to harvest.It also says to plant them 1 inch deep, and about 6 inches apart. Sometimes they talk about "thinning"- this means to pull out some plants after tons of them have sprouted close together. To me, this has always seemed rather wasteful; so instead, I just plant less and a little bit further apart. A good rule of thumb is to plant a seed three times as deep as the size of the seed. A bigger seed needs to be planted deeper in the soil than a tiny seed does. If you planted a tiny carrot seed under one inch of soil, it might never sprout! So, pay attention to the size of your seeds.
There are also some seeds that do better if you soak them before planting. I usually just do this for sweet peas (flowers, not actual peas), but you can also soak most beans or edible peas before planting too.
Send along your questions, and I'll answer them the best I can!