Agreeing with the other answers, "Lecturer" is often the title given to full-time non-tenure track (i.e. contractual) faculty who typically only have instructional duties. Depending on the style of the institution, it may or may not be possible to move into the tenure-track. Lecturer, however, is not always a "dead-end". Some schools have a separate promotion system to reward and promote their non-tenure track faculty (similar to the way you would reward and promote staff). At these institutions there might be ranks, like Lecturer I, Lecturer II, Senior Lecturer, etc.
Disagreeing with the other answers, the term "adjunct" usually refers to a part-time instructor. Adjuncts usually have few if any opportunities for advancement. At many institutions, adjuncts may be distinct from Lectures (as a Lecturer is a full time appointment). My institution confusingly calls full-time and part-time instructors "Lecturer", but then proceeds to treat them as very different types of employee.