Understanding how to query categories in Sanity schema using Groq

export default {
  name: "categories",
  title: "Categories",
  type: "document",
  fields: [
    {
      name: "title",
      title: "Title",
      type: "string",
    },
    {
      name: "slug",
      title: "Slug",
      type: "slug",
      options: {
        source: "title",
        maxLength: 96,
      },
    },
    {
      name: "description",
      title: "Description",
      type: "text",
    },
    {
      name: "featuredImage",
      title: "Featured image",
      type: "image",
      options: {
        hotspot: true,
      },
    },
  ],
};

*[ _type== 'post' && categories->title == 'category name']

*[_type == 'posts' && categories.title match 'category name' ]

*[_type == 'posts' && categories[]->title match 'category name' ]

*[ _type=='posts' && 'category name' in categories[]->title]

&& 'category name' in categories[]->title