These words are two forms of the verb to ride—Ridden is the past-participle and rode is the simple past form:
(a) We rode into town yesterday.
(b) We have ridden into town several times.
(c) This horse has been ridden too many times.
(d) The most often ridden ride at the amusement park is the roller coaster.
To review, the simple past (a) is used when an action simply happens in the past, while the past-participle (b-d) expresses the perfect tense of the verb, describing events that are completed. It can also be used as an adjective, such as in (d).