Don't understand many-to-many relationships

export const User = pgTable("user", {
  id: uuid("id").primaryKey().defaultRandom(),
  username: varchar("username", { length: 255 }).notNull(),
  email: varchar("email", { length: 255 }).notNull(),
  password: varchar("password", { length: 255 }).notNull(),
  createdAt: timestamp("created_at").defaultNow(),
})

export const UserRelations = relations(User, ({ many }) => ({
  userToProject: many(UserToProject, { relationName: "projects" }),
}))

export const Project = pgTable("project", {
  id: uuid("id").primaryKey().defaultRandom(),
  name: varchar("name", { length: 255 }).notNull(),
  website: jsonb("website"),
  createdAt: timestamp("created_at").defaultNow(),
})

export const ProjectRelations = relations(Project, ({ many }) => ({
  userToProject: many(UserToProject, { relationName: "members" }),
}))

export const UserToProject = pgTable(
  "user_to_project",
  {
    userId: uuid("user_id")
      .references(() => User.id)
      .notNull(),
    projectId: uuid("project_id")
      .references(() => Project.id)
      .notNull(),
  },
  (t) => ({
    pk: primaryKey({ columns: [t.userId, t.projectId] }),
  }),
)

export const UserToProjectRelations = relations(UserToProject, ({ one }) => ({
  user: one(User, {
    fields: [UserToProject.userId],
    references: [User.id],
  }),
  project: one(Project, {
    fields: [UserToProject.projectId],
    references: [Project.id],
  }),
}))