Three utensils explain much of what you see when someone prepares matcha.
The chawan is the bowl, the chasen is the bamboo whisk, and the chashaku is the scoop used to portion powdered tea. Each has a distinct job and each is handled in its own way.
Watch the sequence
Look at the scoop as the tea goes into the bowl, then the whisk as it mixes the powder and water. The bowl brings the whole process together and is the utensil a guest is most likely to hold.

Recognize them in a shop
A bowl is more useful when its size and weight suit the way you hold it. If you are buying a whisk, ask the shop how to clean, dry and store it.
Further reading from the Japan Tourism Agency
Explore teaware painting and matcha at Edo Saryo · More Shibuya travel guides