先回答你区别.其实这个很明显的.看下字面的意思就能明白了.
不定式（to+动词原形,之后不带任何成分）可以做,主语,表语：To see is to believe.眼见为实.
作宾语：
如：I can afford to buy a house.类似的词语还有afford,appear,agree,ask,believe,decide,demand,desire,fail,hope,intend,learn,mean,offer,promise,refuse,wish等.
不定式作定语
不定式作定语相当于一个定语从句,它修饰以下几类名词：
⑴由动词派生或转化而来的名词,它们所对应的动词通常有不定式作宾语.这类名词主要有：attempt,claim,decision,plan,promise,intention,need,resolution,tendency,wish,failure,threat等.
Another attempt to climb the mountain will be made next month.
In his speech he expressed his determination to achieve the goal.
⑵由可能与不定式搭配的形容词派生出来的名词.这类名词主要有：anxiety,patience,ability,willingness,ambition等.
Her eagerness to learn a foreign language obvious.
⑶不定式作定语还可用来修饰代词something,anything,everything,nothing.不定式做后置定语.
Do you have anything to send?你有什么东西要寄吗?（不定式to send的动作执行者是you）
Do you have anything to be sent?你有什么要（我或别人）寄的东西吗?不定式to be sent的动作执行者是已被省略的me或someone else）
She has everything to lose and nothing to gain.
⑷由only,last,next,序数词或形容词最高级修饰的名词后常用不定式作定语.
Jim is the only student to answer the question correctly in his class.
You are the last to undertake the blood test.
⑸不定式常作为定语修饰there be结构的真实主语.在there be结构中,用来修饰主语的不定式有时用主动形式,有时用被动形式.当说话人考虑的是必须有人完成某件事时,不定式用主动形式.如果说话人强调的是事情本身必须被完成时,不定式则用被动形式.例如：
There is a lot of work to do.（Somebody has to do the work.）
There is a lot of work to be done.（The work has to be done.）
不定式作状语
不定式作状语相当于一个状语从句,表示形为的目的、结果或原因.
⑴表示目的.在这种情况下,不定式的逻辑主语通常也是全句的主语.
He stayed there to see what would happen.
在强调不定式目的状语时,不定式前可加in order,so as等.如：
She asked me to drive her to the airport in order to catch the 5：00 plane.
He moved the TV set to the meeting-room so as to let everyone watch it.
⑵用so……as to……,such （……） as to……,enough to……,too……to,only to等表示结果,如：
Have you got enough room to seat all of us?
She is too weak to join us in the outing.
⑶将不定式移到句首表示条件,如：
To hear the teacher better,you have to sit in the front.= If you are to hear the teacher better,……
⑷与形容词连用时,大多表示原因.这些形容词主要有：happy,kind,surprised,frightened,angry,shocked,glad,delighted,grieved,disappointed等.
They were surprised to be informed of the news.I‘m glad to hear this.
另外,
不带to 的不定式
1.表示感觉的动词
五看see,notice,watch,observe,look at 三使have,let,make 二听hear,listen to 一感觉feel
He noticed the man enter the room. 他注意到有人进屋了.
They observed her do the experiment. 他们观察她做实验了.
2.help后的不定式可以带to也可以不带to.
Can you help me （to） clean up after the meal? 饭后你能帮我洗碗吗?
3.有些类似于情态动词的词语（如rather than,had better,would rather,might as well等）之后,不定式不带to.如：
We might as well go without him. 我们可以不让他跟去.
You‘d better go now. 你最好现在走.
4.不定式用在介词but,except,besides后时,如果这些介词前有行为动词do的各种形式,那么介词后的不定式不带to,相反则带to.
(1).She could do nothing but cry.
(2).I have no choice but to go.
(3).What do you like to do besides sleep
以上,部分参考教育资源网.
希望对你有用.