In a preschool Mandarin class, kids typically engage in a range of fun and interactive activities designed to introduce them to the language and culture. 
Here’s a general idea of what they might learn:

1. Basic Vocabulary: Children learn simple words and phrases related to everyday activities, such as numbers, colors, animals, family members, and common objects.

2. Simple Sentences: They practice forming basic sentences for everyday communication, like "I want juice" or "This is a cat."

3. Songs and Rhymes: Mandarin is taught through catchy songs and rhymes that help with pronunciation and memorization. These are often accompanied by actions or hand movements.

4. Storytelling: Stories are used to teach new words and concepts in an engaging way. These might include traditional Chinese folktales or modern stories adapted for children.

5. Cultural Elements: Basic elements of Chinese culture, such as festivals (like the Lunar New Year), traditional foods, and customs, are introduced in a way that's accessible and engaging for young children.

6. Games and Activities: Activities like matching games, flashcards, and interactive play help reinforce vocabulary and concepts in a fun and memorable way.

7. Basic Pronunciation and Tones: Children are introduced to the sounds and tones of Mandarin, though this is usually done in a playful manner to make it easier for them to pick up the sounds naturally.

The focus in preschool is very much on making the learning process enjoyable and engaging, using lots of visuals, music, and hands-on activities to create a positive and immersive language experience.