は (wa)
1. Topic marker
Marks the topic of discussion. Can be thought of like “as for” or “regarding”.
As for tomorrow, it's Tuesday = Tomorrow is Tuesday
2. Contrast marker
Shows contrast between several things in a sentence.
I eat meat, but I don't eat fish
The contrasting thing can also be implied rather than explicitly stated.
あの
I didn't see that movie
(Can imply I saw this one)
の (no)
The role of の is to indicate that noun 1 is an attribute of noun 2. This can manifest in a number of different ways, with just a few examples below.
1. Possession
Like the “apostrophe s” or “of” in English.
I's cat = my cat
Geography's teacher = teacher of geography
2. Location
ベッドの
Above the bed = on the bed
3. Characteristic
Wooden bridge
4. Relationship
ペンの
Pen's tip = tip of pen