นี่เลยครับ จาก web microsoft ดูรายละเอียด โดยเฉพาะ ตรงส่วนหนานะ
Microsoft Access provides two field data types (field data type: A characteristic of a field that determines what kind of data it can store. For example, a field whose data type is Text can store data consisting of either text or number characters, but a Number field can store only numerical data.) to store data with text or combinations of text and numbers: Text and Memo.
Use a Text data type to store data such as names, addresses, and any numbers that do not require calculations, such as phone numbers, part numbers, or postal codes. A Text field can store up to 255 characters, but the default field size is 50 characters. The FieldSize property controls the maximum number of characters that can be entered in a Text field.
Use the Memo data type if you need to store more than 255 characters. A Memo field can store up to 65,536 characters. If you want to store formatted text or long documents, you should create an OLE Object field instead of a Memo field.
Both Text and Memo data types store only the characters entered in a field; space characters for unused positions in the field aren't stored.
You can sort or group on a Text field or a Memo field, but Access only uses the first 255 characters when you sort or group on a Memo field.