How do you query documents in MongoDB?

MongoDB's find() method retrieves documents matching a query filter: db.collection.find(query, projection). find() examples: All documents: db.users.find({}); Exact match: db.users.find({ name: "Alice" }); Multiple conditions (implicit AND): db.users.find({ name: "Alice", age: 30 }); Projection (include/exclude fields): db.users.find({}, { name: 1, email: 1, _id: 0 }) — 1 = include, 0 = exclude, can't mix includes and excludes (except _id). findOne(): returns the first matching document (or null). Query operators: Comparison: $eq, $ne, $gt, $gte, $lt, $lte — db.users.find({ age: { $gte: 18, $lt: 65 } }); $in: db.users.find({ status: { $in: ["active", "pending"] } }); $nin: not in list; Logical: $and, $or, $not, $nor; Element: $exists, $type; Evaluation: $regex, $expr, $where; Array: $all, $elemMatch, $size. Sorting: .sort({ age: 1 }) (1 ascending, -1 descending). Limiting and skipping: .limit(10).skip(20) — page 3 of 10. Count: db.users.countDocuments({ active: true }).