I'm not a native speaker, but here's how I understand it.
得 changes the proceeding adjective into an adverb to describe the preceding verb.
地 changes the preceding adjective into an adverb to describe the proceeding verb.
Or in simpler terms, the adverb goes before 地 and after 得, and vice-versa for the verbs.
ex.
快地走 = 走得快 = to walk quickly
With 得, a phrase can take the place of the adverb. For example, 我累得起不来 means "I'm so tired I can't get up" ("I can't get up" takes the place of the adverb). I don't think this is possible with 地.
Incidentally, if you're describing a noun instead of a verb you'd use 的 instead of 地. In spoken language, 的, 地 and 得 are all pronounced 'de'. They're only different in writing. I've observed many native speakers just write 的 for all three. It is possible to omit 的 and 地, but sinc
地 and 得 have other uses as well, so they might not necessarily act as described above. 地 (pronounced as 'di4') can mean 'earth' or 'ground', and it is used in a lot of two character words (ex. 地理 and 地球). 得 is also used in some words (ex. 得到), and 得 (pronounced dei3) can also mean 'must'.
I'm not a native speaker, so I'd take what I've said with a grain of salt.