An easy way to think of this is: Expand = Make Bigger Extend = Make Longer

ex‧pand /ɪkˈspænd/ verb 1. [intransitive and transitive]: to become larger in size, number, or amount, or to make something become larger ⇒ expansion. Antonym : contract: ● Water expands as it freezes. 2. [intransitive and transitive]: if a company, business etc expands, or if someone expands it, they open new shops, factories etc ⇒ expansion: ● The hotel wants to expand its business by adding a swimming pool. 3. [intransitive] literary: to become more confident and start to talk more: ● After a few whiskies he started to expand a little. expand on/upon something phrasal verb to add more details or information to something that you have already said: ● Payne later expanded on his initial statement. [TahlilGaran] Dictionary of Contemporary English

Extend /ɪkˈstend/ verb 1. TIME [intransitive + adverb/preposition,transitive]: to continue for a longer period of time, or to make something last longer: ● Management have agreed to extend the deadline. extend for/into/over etc ● Some of our courses extend over two years. extend something for/by/until something ● The government has extended the ban on the import of beef until June. 2. AREA/DISTANCE [intransitive always + adverb/preposition]: to continue for a particular distance or over a particular area across/over/through etc ● The River Nile extends as far south as Lake Victoria. extend 100 km/30 yards etc (from something) ● The shelf extends 20 cms from the bookcase. 3. SIZE [transitive]: to make a room, building, road etc bigger or longer: ● We plan to extend the kitchen by six feet. 4. INCLUDE/AFFECT a) [intransitive always + adverb/preposition]: to affect or include people, things, or places extend to/beyond etc ● My duties at the school extend beyond just teaching. ● The vote was extended to all women aged 21 and over in 1928. b) [transitive]: to make something affect more people, situations, areas etc than before: ● British Coal is planning to extend its operations in Wales. extend something to somebody/something ● We can extend our insurance cover to travel abroad. 5. OFFER HELP/THANKS [transitive] formal: to officially offer someone help, sympathy, thanks etc extend something to somebody ● We’d like to extend a warm welcome to our French visitors. 6. ARMS/LEGS [transitive]: to stretch out a hand or leg: ● George extended his hand (=offered to shake hands). 7. CONTINUE WINNING [transitive]: to increase the number of points, games etc by which one person or team is ahead of other competitors: ● Manchester United extended their lead at the top of the table to 10 points. 8. FURNITURE [intransitive and transitive]: if a table or ladder extends, it can be made longer ⇒ fold

We use "expand" to refer to an increase in size, volume of an object or the extent of something. Example: The steel rod gained heat and expanded. We may also use "expand" to elaborate on a topic. Example: The lecturer expanded on the theory. We use "extend" to refer to stretching out something or increasing its length. Example: He extended the spring by pulling it. / He extended his hand to congratulate his colleague. Hope this helps. Cheers, Lance

Hi, So 'expand' means to spread something out in terms of width. Like you could say I want to expand my circle of friends (widen it) so expand is to make something more larger or extensive. While extend is to stretch something out like in distance or time. You could say "I want to 'extend' my arm" (stretch it), or "I will ask the teacher to "extend" the time for the homework due date" (longer time). Hope this helps.