It's true that "aim" and "goal" and "objective" can usually be used interchangeably. I would guess that most people don't make distinctions among them.
A: I want to get in to a good college.
B: Yes, of course. What is your aim/ goal/ objective in life? Will the college help you achieve it?
A: You're sure working hard these days! How come?
B: My goal / aim / objective is to become a partner in this firm by the end of next year.
However, in some fields, education for one, "goals" are seen as bigger than "objectives." The objective is a concrete achievement on the way towards achieving a goal.
Here's a definition from a website at the University of Minnesota*:Q) What are the differences between goals and objectives?
"A) Because the two terms are often used interchangeably, confusion sometimes arises. Although both goals and objectives use the language of outcomes, the characteristic that distinguishes goals from objectives is the level of specificity. Goals express intended outcomes in general terms and objectives express them in specific terms. Goals are written in broad, global, and sometimes vague, language. Objectives are statements that describe the intended results of instruction in terms of specific student behaviors...
are statements about general aims or purposes
of education that are broad, long range intended outcomes. Goals are used primarily in policy making and general program planning.Objectives
are brief, clear statements that describe the desired learning outcomes
of instruction. Attention is focused on the specific types of performances that students are expected to demonstrate at the end of instruction."
For another clear presentation of "goals and "objectives," here's a government website: http://www.ed.gov/G2K/teachers/appndx5.html
In more general English, the American Heritage Dictionary has this usage note at "intention":
SYNONYMS intention, intent, purpose, goal, end, aim, object, objective
. These nouns refer to what one plans to do or achieve. Intention
simply signifies a course of action that one proposes to follow: It is my intention to take a vacation next month. Intent
more strongly implies deliberateness: The executor complied with the testator's intent.
strengthens the idea of resolution or determination: "His purpose was to discover how long these guests intended to stay"
(Joseph Conrad). Goal
may suggest an idealistic or long-term purpose: The college's goal was to raise ten million dollars for a new library.
suggests a long-range goal: The candidate wanted to win and pursued every means to achieve that end.
stresses the direction one's efforts take in pursuit of an end: The aim of most students is to graduate
is an end that one tries to carry out: The object of chess is to capture your opponent's king. Objective
often implies that the end or goal can be reached: The report outlines the committee's objectives
**The American Heritage Dictionary of the English Language, Fourth Edition. Houghton Mifflin Company. 2004